A man who served nearly 17 years in jail for killing his grandmother set a house and car on fire this morning in upstate New York and then began shooting at emergency personnel who showed up, killing two firefighters, police said.

In all, William Spengler, 62, shot four firefighters, killing two and severely injuring two more after setting his "trap," police said.

An off-duty police officer from Greece, N.Y., who responded to the scene early in the morning of Christmas Eve also was injured today.

"It was a trap," said Webster, N.Y., Police Chief Gerald L. Pickering, "set by Mr. Spengler who laid in wait and shot first responders."

Spengler, who was released from prison in 1998, was found dead at the scene following a shootout with police. He was believed to have killed himself with a bullet to the head.

As a convicted felon, Spengler would not have been allowed to own guns legally. Police were working to determine the types of weapons he used and how he obtained them, Pickering said.

Spengler was convicted of manslaughter in 1981 for "beating his 92-year-old grandmother with a hammer," according to state prison documents.

Several weapons were used, Pickering said, and, "probably a rifle was used to inflict wounds of the first responders.

"I know many people are going to be asking if they were assault rifles," Pickering said

There has been a week-long national debate about such weapons after one was used in a tragic school shooting in Newtown, Conn. on Dec. 14.

Four firefighters, two on a ladder truck and two more in their own vehicles, responded to 911 calls around 5:30 a.m. Monday morning. Spengler is believed to have hidden behind an elevated berm, shooting down on the firefighters and later police.

"Upon arrival, all [the firefighters] drew fire. All four were shot on the scene," Pickering said. "One was able to flee the scene. The other three were pinned down."

Police believe Spengler's sister may have been inside the home, and that he set it on fire.

The blaze spread, engulfing three nearby homes and damaging three more on a sleepy street next to Lake Ontario that police described as a quiet vacation community. The fire was not put under control until late this afternoon.

SWAT team officers used an armored personnel carrier to evacuate 33 residents from homes in the area.

Among the dead firefighters was Lt. Michael Chiapperini, a 20-year veteran of the Webster Police Department and "lifetime firefighter," according to Pickering. Chiapperini was a spokesman for the police department, ABC News affiliate WHAM reported.

Police identified the other firefighter killed as Tomasz Kaczowka, who also worked as a 911 dispatcher.

The chief, choking up, called the incident that shattered the quiet before 6 a.m. on Christmas Eve morning "terrible."

"People get up in the middle of the night to fight fires," he said. "They don't expect to get shot and killed."

Two surviving firefighters were in the intensive care unit at Strong Memorial Hospital in Rochester, N.Y. Both men were awake and breathing on their own after surgery and were in what doctors are calling "guarded condition."

Joseph Hofsetter was shot once. He sustained an injury to his pelvis and has "a long road to recovery," said Dr. Nicole A. Stassen, a trauma physician.

The second firefighter, Theodore Scardino, was shot twice and received injuries to his left shoulder and left lung, as well as a knee.

New York Gov. Andrew Cuomo released a statement calling the attack a "senseless act of violence" and the first responders "true heroes."